The purpose of the research project is to obtain basic neuroanatomical data concerning the organization of the neurons and tracts of the lower auditory pathway of the cat. Of principal concern are the types of neurons, the structure of the afferent plexus and the axonal projections of the various subdivisions of the cochlear nucleus. By means of correlating data obtained by a variety of light microscopic techniques, including rapid Golgi, Nauta degeneration, and retrograde axonal transport, the precise source of the several distinct fiber projections of the cochlear nuclei will be determined.